Chemical reinforcing holders for glass substrate

ABSTRACT

The present invention provides a holder that prevents a glass substrate from deforming during a chemical reinforcing process. The holder includes supporting members, each of which has a plurality of supporting concave portions. The supporting members are formed from a flat plate having a constant thickness so as not to have a portion having high thermal capacity. When the glass substrate is cooled, a thermal stress is not applied to the glass substrate.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a holder for supporting a glasssubstrate for an information recording medium, such as a magnetic disc,a magneto-optical disc or an optical disc. Particularly, the inventionrelates to a holder for a chemical reinforcing process for immersing aglass substrate in a chemical reinforcing liquid.

[0002] Japanese Laid-Open Patent Publication No. Hei 7-176045 disclosesa conventional holder for immersing a glass substrate in a chemicalreinforcement tank in order to chemically reinforce the glass substrate.The conventional holder is formed by three rods, which are parallel withone another, and two side plates for fixing the ends of the rods.Annular beads are inserted into the respective rods and are fixed to therods with predetermined intervals. A flat recess is partitioned betweenadjacent beads. The flat recesses of the three rods receive three outeredge portions of a glass substrate, respectively. As a result, the glasssubstrate is supported by the holder.

[0003] Chemical reinforcement of a glass substrate will be described. Aholder which holds glass substrates is put into a tank which stores achemical reinforcing liquid containing a potassium nitrate (KNO₃)liquid. After predetermined time, the holder is taken out from the tank,and the glass substrates and the holder are cooled to a roomtemperature.

[0004] In the conventional holder, since beads, each of which has arelatively large thermal capacity, are fixed to the rods, a coolingspeed of the glass substrate at portions that contact with the rods islower than that of the other portions in the glass substrate. For thisreason, during the cooling, contraction of the portions contacting withthe rods is small, but contraction of the other parts are large.Therefore, the conventional holder has a problem that a glass substrateis distorted.

SUMMARY OF THE INVENTION

[0005] An objective of the present invention is to provide a holder forglass substrates without distorting the glass substrate in chemicalreinforcing process.

[0006] In order to achieve the above objective, the present inventionprovides a holder for holding glass substrates for an informationrecording medium and for immersing the glass substrates in a heatedchemical reinforcing liquid. The holder includes a frame, and aplurality of supporting members mounted on the frame. Each of thesupporting members has a plurality of supporting concave portions forreceiving outer edges of the glass substrates, respectively, andthickness of the supporting members is constant.

[0007] A further perspective of the present invention is a holder forimmersing a glass substrate in a chemical reinforcing liquid. The holderincludes a frame, first, second and third supporting plates mounted onthe frame. The first supporting plate has a first serrate portion thatdefines a first concave portion for receiving a first portion of theglass substrate. The second supporting plate has a second serrateportion that defines a second concave portion for receiving a secondportion of the glass substrate. The third supporting plate has a thirdserrate portion that defines a third concave portion for receiving abottom portion of the glass substrate.

[0008] A further perspective of the present invention is a holder forimmersing a glass substrate in a chemical reinforcing liquid. The holderincludes a frame, first, second and third supporting wires mounted onthe frame. The first supporting wire has a first serrate portion thatdefines a first concave portion for receiving a first portion of theglass substrate. The second supporting wire has a second serrate portionthat defines a second concave portion for receiving a second portion ofthe glass substrate. The third supporting wire has a third serrateportion that defines a third concave portion for receiving a bottomportion of the glass substrate.

[0009] Other aspects and advantages of the present invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The features of the present invention that are believed to benovel are set forth with particularity in the appended claims. Theinvention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

[0011]FIG. 1 is a partially broken perspective view of a holderaccording to one embodiment of the present invention.

[0012]FIG. 2 is a perspective view of a supporting member.

[0013]FIG. 3A is a plan view of the supporting member.

[0014]FIG. 3B is a cross-sectional view taken along the line 3B-3B ofFIG. 3A.

[0015]FIGS. 4 and 5 are plan view and side view of the supporting memberwhich supports a glass substrate.

[0016]FIGS. 6A, 6B and 6C show modified examples of the supportingmember.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A holder for a chemical reinforcing process according to oneembodiment of the present invention will be described below.

[0018] As shown in FIG. 1, a holder 11 has frames 12 and 13, first,second and third supporting members 15 a, 15 b and 15 c fixed to theframes. The frames 12 and 13 include two side plates 12 and fourelongate connecting plates 13 which are mounted in the four corners ofthe side plates 12, respectively, and connect both the side plates 12.It is preferred that the side plates 12 are made of metal such as nickelalloy, stainless steel, pure titanium or titanium alloy.

[0019] Near the center of three sides of each side plate 12 are formedwith three supporting holes or slits 14, respectively. The ends of thesupporting members 15 a, 15 b and 15 c are inserted into the two slits14 opposed to each other, respectively. Each one end of the supportingmembers 15 a, 15 b and 15 c is welded with one side plate 12, and eachother end of the supporting members 15 a, 15 b and 15 c is not weldedwith each slit 14 of the other side plate 12 to be supported thereto. Insuch a manner, the supporting members 15 a, 15 b and 15 c are fixedbetween both the side plates 12.

[0020] Each of the supporting members 15 a, 15 b and 15 c is made of aflat thin plate. Each of the supporting members 15 a, 15 b and 15 c isformed of a metal material such as nickel alloy, stainless steel, puretitanium or titanium alloy. Of these metal materials, nickel alloyhaving good corrosion resistance, mechanical property andprocessability, or a titanium alloy with high corrosion resistance,small specific gravity and small thermal capacity is preferred. Puretitanium is more preferable.

[0021] As shown in FIG. 1, one side of each of the supporting members 15a, 15 b and 15 c is formed with jagged serrate portion 16 a, 16 b and 16c, respectively. Namely, the serrate portions 16 a, 16 b and 16 c areflush with the relating supporting members 15 a, 15 b and 15 c. Theserrate portions 16 a, 16 b and 16 c include a plurality of supportingconcave portions 18 a, 18 b and 18 c, respectively. The serrate portion16 a of the first or left side supporting member 15 a is opposed to theserrate portion 16 b of the second or right side supporting member 15 b.The serrate portion 16 c of the third or lower supporting member 15 cfaces upward.

[0022]FIG. 2 is an enlarged diagram of the left side supporting member15 a. The right side and the lower supporting members 15 b and 15 c havethe same structure shown in FIG. 2. The plural supporting concaveportions 18 a, 18 b and 18 c are defined by ridgelines 16r of theserrate portions 16 a, 16 b and 16 c. The ridgeline 16 r is chamfered bya wet barrel polishing process, so that a burr is removed. Therefore,outer surfaces of the serrate portions 16 a, 16 b and 16 c are smooth.As shown in FIG. 3B, it is preferred that the ridgeline 16 r is of acurved surface type.

[0023] As shown in FIG. 5, a glass substrate 17 is a disc having acircular hole at its center which is used as a substrate for aninformation recording medium such as a magnetic disc, a magneto-opticaldisc or an optical disc. A glass material forming the glass substrate 17includes sodalime glass mainly containing silicon dioxide (SiO₂), sodiumoxide (Na₂O) and calcium oxide (CaO); aluminosilicate glass mainlycontaining SiO₂, aluminum oxide (Al₂O₃) and R₂O (R indicates potassium(K), sodium (Na), lithium (Li)); borosilicate glass; lithium oxide(Li₂O)—SiO₂ glass; Li₂O—Al₂O₃—SiO₂ glass; and R′O—Al₂O₃—SiO₂ glass (R′indicates magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba)).Moreover, the glass material also includes a glass for chemicalreinforcing process where zirconium oxide (ZrO₂) or titanium oxide(TiO₂) is added to these glass materials. As shown in FIG. 4, an outerperipheral edge of the glass substrate 17 is chamfered.

[0024] As shown in FIG. 4, the three supporting concave portions 18 a,18 b and 18 c are arranged on the same plane so that the outer edge ofthe glass substrate 17 is received by the three supporting concaveportions 18 a, 18 b and 18 c. As shown in FIG. 1, the holder 11 can holda plurality of glass substrates 17 in a vertically standing state.

[0025] One glass substrate 17 is inserted among the three supportingmembers 15 a, 15 b and 15 c. As shown in FIGS. 4 and 5, a left edgeportion of the glass substrate 17 is supported by the left supportingmember 15 a, and the bottom portion of the glass substrate 17 issupported by the supporting member 15 c. A right outer peripheralsurface of the glass substrate 17 is separated by a gap L from thesupporting concave portion 18 b of the right supporting member 15 b.Preferably the gap L is 0.1 to 0.5 mm at normal temperature. In the casewhere the gap L is less than 0.1 mm, when the glass substrate 17 and theholder 11 are immersed in a chemical reinforcing liquid, there is a fearthat the glass substrate 17 is pressed strongly between the supportingmembers 15 a, 15 b and 15 c due to thermal expansion. In the case wherethe gap L is larger than 0.5 mm, the glass substrate 17 is not stablysupported, and when it is oscillated, there is a fear that the glasssubstrate 17 may collide strongly with the supporting members 15 a, 15 band 15 c and be damaged.

[0026] As shown in FIG. 5, the glass substrate 17 comes in contact withthe left supporting member 15 a in a first position (supporting point)19. It is preferred that an angle (lower angle) θ between a plane whichconnects the supporting point 19 with a center 17 c of the glasssubstrate 17 and a plane which connects the left supporting member 15 awith the center 17 c of the glass substrate 17 is 160 to 180°. In otherwords, it is preferred that the left supporting member 15 a and theright supporting member 15 b are separated from the lower supportingmember 15 c by 80 to 90° in a circumferential direction of the glasssubstrate 17 with respect to the center 17 c of the glass substrate 17.For example, the angle θ between the left and right supporting members15 a and 15 b is 180° in a position indicated by a solid line in FIG. 5.In a position indicated by alternate long and two short dashes line, theangle θ between the left and right supporting members 15 a and 15 b is160°.

[0027] In the case where the lower angle θ is less than 160°, there is afear that the glass substrate 17 is oscillated relatively greatly due tovibration and is damaged. As the lower angle θ is smaller, thesupporting of the glass substrate 17 becomes more unstable. Meanwhile,when the lower angle θ exceeds 180°, it is difficult to insert the glasssubstrate 17 into the holder 11.

[0028] As shown in FIG. 4, the bottom portions of the supporting concaveportions 18 a, 18 b and 18 c have slightly larger width than a thicknessof the glass substrate 17. As shown in FIG. 5, the lower supportingmember 15 c is thicker than the left and right supporting members 15 aand 15 b.

[0029] Next, the chemical reinforcing process will be described.

[0030] A heated chemical reinforcing liquid is stored in a chemicalreinforcement tank (not shown). Chemical reinforcement salt is, forexample, KNO₃ or sodium nitrate (NaNO₃). The chemical reinforcing liquidcontains sodium ions (Na⁺) or potassium ions (K⁺) which are monovalentmetal ions having a relatively large ion radius. The holder 11 holdingthe glass substrate 17 is arranged in a cage, not shown, and the cage isput into the chemical reinforcement tank. As a result, the glasssubstrate 17 and the holder 11 are immersed in the heated chemicalreinforcing liquid.

[0031] Metal ions having relatively small radius such as lithium ions(Li⁺) and Na⁺exist on the surface layer of the glass substrate 17. Whenthe glass substrate 17 is immersed in the chemical reinforcing liquid,metal ions with relatively small surface layer are exchanged withrelatively large metal ions in the chemical reinforcing liquid. Withthis ion exchange, a compression stress is applied to the surface layerof the glass substrate 17. As a result, the glass substrate 17 ischemically reinforced.

[0032] In the case where the glass substrate 17 is subjected to chemicalreinforcing process, firstly a plurality of glass substrates 17 areinserted between the supporting concave portions 18 a and 18 b of theleft and right supporting members 15 a and 15 b from above the holder11, so that the bottom portions of the glass substrates 17 are broughtinto contact with the supporting concave portions 18 c of the lowersupporting member 15 c. As a result, the plural glass substrates 17 areheld at the holder 11 in the vertically standing state. A plurality ofholders 11 are housed in the cage, not shown. The cage is put into thechemical reinforcement tank where the chemical reinforcing liquid isstored. As a result, the plural glass substrates 17 and holders 11 areimmersed in the chemical reinforcing liquid.

[0033] In one embodiment, the chemical reinforcing liquid is obtained byheating KNO₃ and NaNO₃. A temperature of the chemical reinforcing liquidis preferably lower than a distortion point of a glass material by about50 to 150° C. More preferably, the temperature of the chemicalreinforcing liquid is about 350 to 400° C.

[0034] The glass substrates 17 are immersed in the chemical reinforcingliquid for predetermined time. During the immersing, Li⁺on the surfacelayer of the glass substrate 17 is ion-exchanged with Na⁺or K⁺, andNa⁺on the surface layer of the glass substrate 17 is ion-exchanged withK⁺. The strength of the glass substrate 17 is improved by the ionexchange. As a result, when the glass substrate 17 is used for aninformation recording medium, its breakage due to high-speed rotationcan be prevented.

[0035] In addition, during the immersing, the supporting members 15 a,15 b and 15 c and the glass substrate 17 are thermally expanded(alternate long and two short dashes line in FIG. 5). The glasssubstrate 17 is separated by a gap L from the bottom portion of theright supporting concave portion 18 b at normal temperature. Even if theglass substrate 17 and the supporting members 15 a, 15 b and 15 c areexpanded, the gap L is set so that the glass substrate 17 does not comein contact with both the left and right supporting members 15 a and 15b. For this reason, a deformation of the glass substrate 17 isprevented.

[0036] After the immersing for predetermined time, the cage is taken outfrom the chemical reinforcement tank, the glass substrates 17 and theholders 11 are cooled to normal temperature. As a result, the chemicalreinforcement of the glass substrates 17 is completed.

[0037] According to one embodiment, the following advantages areobtained.

[0038] The supporting members 15 a, 15 b and 15 c are relatively thinplate materials. For this reason, the supporting members 15 a, 15 b and15 c do not have portions with large thermal capacity unlikeconventional annular beads. Therefore, while the glass substrates 17 andthe holders 11 are being cooled, a thermal stress which is generated onthe glass substrate 17 is reduced. A distortion is prevented by thechemical reinforcing process from occurring on the glass substrate 17.As a result, the flat and chemically reinforced glass substrate 17 isobtained.

[0039] The serrate portions 16 a, 16 b and 16 c which define the pluralsupporting concave portions 18 a, 18 b and 18 c are formed on each oneside of the supporting members 15 a, 15 b and 15 c. As a result, theholder 11 can hold a plurality of glass substrates 17. Moreover,insertion and taking-out of the glass substrate 17 can be easily carriedout.

[0040] Ridgelines 16 r of the serrate portions 16 a, 16 b and 16 cundergo the wet barrel polishing process. For this reason, a burr on thesurfaces of the serrate portions 16 a, 16 b and 16 c is removed, and theridgeline 16 r is formed into a smooth curved surface. Therefore, adamage such as a break or a crack does not occur on the glass substrate17, and the glass substrate 17 can be easily inserted between the leftand right supporting members 15 a and 15 b.

[0041] The left and the right supporting members 15 a and 15 b areseparated by the lower angle θ, which is set within the range of 160 to180°, against the center 17 c of the glass substrate 17. For thisreason, the glass substrates 17 can be inserted into the holder 11easily, and the glass substrates 17 can be supported by the holder 11stably. Moreover, even if the holder 11 is vibrated, the glass substrate17 is prevented from being oscillated and damaged.

[0042] When two places of the glass substrate 17 (first position (19)and bottom portion) come in contact with the supporting members 15 a and15 c, the glass substrate 17 is separated by a gap L from the supportingmember 15 b. The gap L is set at 0.1 to 0.5 mm at normal temperature.For this reason, the holder 11 and the glass substrate 17 are heated,and even if the supporting members 15 a, 15 b and 15 c and the glasssubstrate 17 are thermally expanded, the glass substrate 17 is notstrongly pressed by the supporting members 15 a, 15 b and 15 c. Further,even if the holder 11 is vibrated, the glass substrate 17 is preventedfrom being oscillated to be damaged.

[0043] The supporting members 15 a, 15 b and 15 c are welded with oneside plate 12 at each end of their longitudinal direction, and the otherends of the supporting members 15 a, 15 and 15 c are not welded to theother side plate 12 but are only inserted into the slits 14. For thisreason, even if the holder 11 is heated, the supporting members 15 a, 15b and 15 c are not distorted. In other words, the frames 12 and 13 arepositioned so as to allow thermal expansion of the supporting members 15a, 15 b and 15 c.

[0044] Next, the present invention will be described in more detail byway of Examples.

EXAMPLES 1 to 7

[0045] In Examples 1 to 3, a holder 11 having supporting members 15 a,15 b and 15 c where ridgelines 16 r of serrate portions 16 a, 16 b and16 c were not polished was used. Fifty glass substrates 17 were insertedinto and taken out of the holder 11, and this process repeated fivetimes.

[0046] In Examples 4 to 7, a holder 11 having a supporting member 15where ridgelines 16 r of serrate portions 16 a, 16 b and 16 c werepolished by a wet barrel polishing process was used. One hundred glasssubstrates 17 were inserted into/taken out of the holder 11 five times.

[0047] A damage incidence on the glass substrate 17 was measured. Theresults are shown in Table 1. In Examples 1 to 3, the results are anaverage value of the fifty glass substrates 17, and in Examples 4 to 7,the results are an average value of the one hundred glass substrates 17.TABLE 1 Example 1 2 3 4 5 6 7 Damage 10.67 27.33 5.33 0.33 0.67 0.001.00 incidence (%)

[0048] Damage incidence in Examples 1 to 3 was relatively low. Damageincidence in Examples 4 to 7 was lower than that in Examples 1 to 3.This is because the ridgelines 16 r of the serrate portions 16 a, 16 band 16 c are polished by the wet barrel polishing process.

[0049] It should be apparent to those skilled in the art that thepresent invention may be embodied in many other specific forms withoutdeparting from the spirit or scope of the invention. Particularly, itshould be understood that the present invention may be embodied in thefollowing forms.

[0050] Three supporting members 15 a, 15 b and 15 c form one set and twoor more sets of them may be mounted on the side plates 12. In this case,the holder 11 can hold two or more rows of plural glass substrates 17.The number and size of the connecting plates 13 and mounting positionsfor the side plates 12 are changed suitably.

[0051] The supporting members 15 a, 15 b and 15 c may be fixed to oneside plate 12 by a lock mechanism or the like other than the weldingmethod.

[0052] It is preferred that the bottom portions of the supportingconcave portions 18 a, 18 b and 18 c are polished by a method such asthe wet barrel polishing process, but need not be polished. In thiscase, it is preferable that side portions which are contiguous with thebottom portions of the supporting concave portions 18 a, 18 b and 18 care polished.

[0053] As shown in FIG. 4, in one embodiment, bottom portions of thesupporting concave portions 18 a, 18 b and 18 c of the left and rightsupporting members 15 a and 15 b are flat, but approximatelysemicircular protrusions may be provided on the bottom portions of thesupporting concave portions 18 a, 18 b and 18 c, respectively. In thiscase, since the protrusions come in contact with the outer peripheralsurface at one point, occurrence of distortion on the glass substrate 17can be further suppressed. Therefore, flatness of the glass substrate 17can be maintained more satisfactorily.

[0054] The supporting members 15 a, 15 b and 15 c may be made of a linematerial such as a wire as shown in FIGS. 6A, 6B and 6C. FIGS. 6A, 6Band 6C show modified examples of one supporting member 15 a, but theremaining supporting members 15 b and 15 c may have the same structure.

[0055] In the supporting member 15 a (15 b, 15 c) shown in FIG. 6A, aline material is bent with constant intervals in one plane so that aplurality of supporting concave portions 18 a (18 b, 18 c) are formed.The width of the bottom portion of the supporting concave portion 18 a(18 b, 18 c) adjacent to the outer edge of the glass substrate 17 isslightly larger than the thickness of the glass substrate 17. Two sideportions which are contiguous with the bottom portion of the supportingconcave portion 18 a (18 b, 18 c) approach closer to each other as theyare closer to the bottom portion. Namely, the supporting concaveportions 18 a (18 b, 18 c) are formed into a trapezoid shape.

[0056] In the supporting member 15 a (15 b, 15 c) shown in FIG. 6B, aline material is bent so that a plurality of wave-shaped supportingconcave portions 18 a (18 b, 18 c) are formed.

[0057] In the supporting member 15 a (15 b, 15 c) shown in FIG. 6C, aline material is bent with constant intervals on one plane with itsplane having an approximately semi-elliptic shape, so that a pluralityof supporting concave portions 18 a (18 b, 18 c) are formed. In thiscase, the bottom portions of the supporting concave portions 18 a (18 b,18 c) have linear shape, and two side portions which are contiguous withthe bottom portion gently approach each other as they are closer to thebottom portions.

[0058] A surface of the supporting member 15 a (15 b, 15 c) made of alinear line material is notched with constant intervals so that aplurality of supporting concave portions 18 a (18 b, 18 c) may beformed. In this case, it is preferred that the width of the bottomportion of the supporting concave portion 18 a (18 b, 18 c) is slightlylarger than the thickness of the glass substrate 17 and two sideportions which are contiguous with the bottom portion approach closer toeach other as they are closer to the bottom portions.

[0059] The present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

What is claimed is:
 1. A holder for holding glass substrates for aninformation recording medium and for immersing the glass substrates in aheated chemical reinforcing liquid, the holder comprising: a frame; anda plurality of supporting members mounted on the frame, wherein each ofthe supporting members has a plurality of supporting concave portionsfor receiving outer edges of the glass substrates, respectively, andwherein thickness of the supporting members is constant.
 2. The holderaccording to claim 1, wherein the supporting members are plates havingone edge formed with serrate portions including the plurality ofsupporting concave portions.
 3. The holder according to claim 1, whereineach of the supporting members is a line member which is bent so thatthe supporting concave portions are formed.
 4. The holder according toclaim 1, wherein each of the supporting members has a ridgeline whichdefines the supporting concave portions, and wherein the ridgeline ischamfered.
 5. The holder according to claim 4, wherein the ridgeline ischamfered by barrel polishing.
 6. The holder according to claim 1,wherein the glass substrate is held vertically and the supportingmembers include: a first supporting member which contacts with a firstposition of the outer edge of each glass substrate; a second supportingmember which is provided so as to be separated by a predetermineddistance from the outer edge of the glass substrate in a second positionseparated from the first position of the glass substrate by 160 to 180°in a circumferential direction of the glass substrate with respect tothe center of the glass substrate; and a third supporting member forsupporting the lower end of each glass substrate.
 7. The holderaccording to claim 6, wherein the predetermined distance is set at 0.1to 0.5 mm at normal temperature.
 8. The holder according to claim 1,wherein the frame includes two side plates, each of which has aplurality of slits, and a connecting member for connecting the two sideplates, and wherein both ends of the supporting members are insertedinto the plurality of slits of the two side plates, respectively.
 9. Theholder according to claim 8, wherein one end of each of the supportingmembers is fixed to one of the two side plates, and the other end ofeach of the supporting members is mounted on the other side platemovably.
 10. The holder according to claim 1, wherein each of the pluralsupporting members is formed so that the supporting concave portions arearranged in a plane.
 11. The holder according to claim 1, wherein thechemical reinforcing liquid contains second ions which have an ionradius larger than an ion radius of first ions existing in a surfacelayer of each of the glass substrates, and the holder is used toexchange the first ions with the second ions and chemically reinforcethe glass substrates.
 12. A holder for immersing a glass substrate in achemical reinforcing liquid, the holder comprising: a frame; a firstsupporting plate mounted on the frame, the first supporting plate havinga first serrate portion that defines a first concave portion forreceiving a first portion of the glass substrate; a second supportingplate mounted on the frame, the second supporting plate having a secondserrate portion that defines a second concave portion for receiving asecond portion of the glass substrate; and a third supporting platemounted on the frame, the third supporting plate having a third serrateportion that defines a third concave portion for receiving a bottomportion of the glass substrate.
 13. The holder according to claim 12,wherein the third supporting plate is thicker than the first and secondsupporting plates.
 14. The holder according to claim 13, wherein thefirst, second and third supporting plates have ridgelines that definesthe relating concave portions, respectively, and the ridgelines arechamfered.
 15. The holder according to claim 12, wherein the first andsecond supporting members are separated by 160 to 180° in acircumferential direction with respect to the center of the glasssubstrate.
 16. The holder according to claim 12, wherein the thirdsupporting member is separated from the first and second supportingmembers by 80 to 90° in a circumferential direction with respect thecenter of the glass substrate.
 17. The holder according to claim 12,wherein the frame is connected with the first, second and thirdsupporting members so as to allow thermal expansion of the first, secondand third supporting members.
 18. A holder for immersing a glasssubstrate in a chemical reinforcing liquid, the holder comprising: aframe: a first supporting wire mounted on the frame, the firstsupporting wire having a first serrate portion that defines a firstconcave portion for receiving a first portion of the glass substrate; asecond supporting wire mounted on the frame, the second supporting wirehaving a second serrate portion that defines a second concave portionfor receiving a second portion of the glass substrate; and a thirdsupporting wire mounted on the frame, the third supporting wire having athird serrate portion that defines a third concave portion for receivinga bottom portion of the glass substrate.
 19. The holder according toclaim 18, wherein the first, second and third serrate portions areformed by bending the first, second and third supporting wires.
 20. Theholder according to claim 19, wherein the third supporting wire isthicker than the first and second supporting wires.